Fun Riddles

Question: No matter how much rain comes down on it it won't get any wetter.

What is it?

Question: I can run but never walk. Wherever I go, thought are close behind me.

What am I?

Question: There was once three trees. The first tree did whatever the third tree did, and the third tree did what ever the second one does. What happens if tree number two gets cut down?

Question: When do you go at red, but stop at green?

Question: Why don't mountains catch colds?